1. Field of the Invention
The present invention relates to a signal generating method and a radar system, and more particularly, to a signal generating method and a radar system capable of differentiating ghost targets, reducing false detection rate significantly, providing high speed resolution and high distance resolution as well as simplifying the detection algorithm.
2. Description of the Prior Art
Generally, different forms of radar transmission waves correspond to different detection methods, and the forms of radar transmission waves and the corresponding detection methods are important factors that affect performance of entire radar systems. In the prior art, transmission waves composed of linear frequency modulated continuous waves (LFMCWs) can be used for estimating distance and speed of a target, and therefore are often applied to a radar system to generate the transmission signal.
Nevertheless, in an environment with multiple targets (i.e. a noisy environment), interference among radar systems has been greatly increased due to a proliferation of the conventional radar systems. In other words, a signal received by a radar system may be a transmission signal transmitted by another of the same kind of radar system on a target, but not a reflected signal of the radar system itself, which may result in false detection. For example, if any two vehicles respectively equipped with a radar system A and a radar system B using the same form of transmission waves exist in an environment, wherein a distance between the radar system A and the radar system B is R, the transmission signal of the radar system B may interfere with the reflected signal of the radar system A. That is, the radar system A may receive two receiving signals in the same time, including a signal transmitted by the radar system A and then reflected by the radar system B, and a transmission signal of the radar system B. For the radar system A, the transmission signal of the radar system B may interfere with the receiving signal (i.e. the reflected signal) of the radar system A. When a receiver of the radar system A performs related processing for the receiving signals, the radar system A may be misled to come out a wrong result that shows two targets exist in the environment, since the relativity of these two receiving signals and the transmission signal of the radar system A are quite high. In such a condition, one target is a real target where the radar system B is located with the distance R; however, the other target is a ghost target with a distance R/2. The ghost target causes false detection of the radar system, and the false detection rate may be as high as 50%. When more radar systems of the same kind exist in the environment, the false detection rate becomes even higher.
On the other hand, the radar system should be able to detect the distance and the speed of the target while achieving high resolution and accuracy. Besides, there are many challenges for designing a radar system, such as requirements to distinguish moving targets and steady targets, and to recognize multiple targets and ghost targets. In addition, the conventional detection algorithm may be too complex and need to be simplified. Therefore, how to provide a radar system with improved detection performance in a noisy environment and with high-speed and long-distance resolution has become a common goal in the industry.